43 farmers with milk showing positive Wisconsin mastitis test results were divided into 3 groups: group (i) had an extension meeting on mastitis plus four 3-monthly visits to their farms; group (ii) had meeting but no farm visit; and group (iii) were given no information. During 1 yr incidence of mastitis in groups (i), (ii) and (iii) fell from 45, 41 and 56% resp. to 28, 27 and 40%. Proportion of farms practising teat dipping rose from an av. of 14% to 69, 45 and 29% resp..